Method of osteosyntheses or arthrodesis of two-bone parts, in particular of the hand and / or foot

ABSTRACT

In one embodiment, the present invention is a fixation device including a median zone having a substantially triangular shape; a first fixation zone including first and second tabs that, in a separated configuration, extend away from each other from an end of the median zone, the first fixation zone having a first region adjacent the median zone and a second region adjacent the first region. Also, within the first region of the first fixation zone, an inner surface of each of the first and second tabs of the first fixation zone extends outwardly and proximally from the median zone to a first point to form an arch, and from the first point, the inner surface of each of the first and second tabs extends toward a second point. Further, within the second region of the first fixation zone, the inner surface of each of the first and second tabs of the first fixation zone extends outwardly from each second point to a respective third point so that the inner surface of each of the first and second tabs from the second point to the third point is arcuate and convex.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/896,894, filed May 17, 2013, which is a continuation of U.S.application Ser. No. 11/911,405, filed Mar. 17, 2008, which is a USnational phase of PCT Publication PCT/FR2006/050345, filed 12 Apr. 2006,published 19 Oct. 2006 as WO2006/109004, and claiming the priority ofFrench Application No. 0550957, filed Apr. 14, 2005, whose entiredisclosures are herewith incorporated by reference.

FIELD OF THE INVENTION

The invention relates to the technical field of orthopaedic implants,particularly for arthrodesis and osteosyntheses.

It may be recalled that the object of an arthrodesis is to obtain verygood stability both primary and secondary, and to place, or to maintain,in compression, two bone parts or bone fragments that should beconsolidated. Stability is a critical factor for obtainingconsolidation, while minimizing the attendant problems such as pain,swelling, etc. The compressive action serves to consolidate theosteotomy more rapidly in the position selected by the surgeon duringthe operation.

Various technical solutions have been proposed for carrying out anarthrodesis, particularly in the foot, the hand, the wrist, etc. Mentioncan be made, for example, of basic staples without shape memory which donot produce a compression, as opposed to memory staples which serve toplace the two bone parts to be consolidated in compression, whichcorresponds to the objective.

However, to obtain satisfactory stability, it is necessary to place two,or even three staples, in different planes. This increases thedimensions considerably, thereby limiting applications(metacarpo-phalangeal joint, for example).

Extramedullary plates and screws have also been proposed, requiring analternatively large dimension. In this respect, their miniaturization isdifficult to conceive, because this could raise problems of strength andstiffness. Some types of screws can be used in intramedullaryosteosynthesis, but they raise positioning difficulties (passage throughthe pad in particular).

Use can also be made of pins which have a smaller size. However, thestability obtained is unsatisfactory and it is necessary to withdrawthem.

Intramedullary nails are also known, but they require supplementarystapling in order to prevent the bone parts to be joined from rotatingrelative to each other.

OBJECT OF THE INVENTION

It is the object of the invention to remedy these drawbacks simply,safely, effectively and efficiently.

The problem that the invention proposes to solve is to permit thefixation of two bone parts to one another, rigidly with dynamic andretentive compression, in order to obtain a reliable and rapidosteosynthesis.

SUMMARY OF THE INVENTION

To solve such a problem, an intramedullary arthrodesis element has beendesigned and developed which consists of a body with an elongated shapehaving, in succession, from one of its ends, a fixation zone cooperatingwith one of the bone parts to be immobilized, a median zone suitable forwithstanding shear and bending stresses, and a fixation zone in theother bone part to be immobilized, each of the fixation zones beingprofiled and made from a material suitable for enabling introductioninto the bone parts without a finger- or toe-tip approach, followed by afixation in the bone parts, while avoiding any rotational movement,withstanding the tensile stresses, and maintaining a compressive force.

The invention has a particularly advantageous application, which canhowever not be considered as limiting, for the preparation ofarthrodesis in the proximal and median phalanges, for proximalinterphalangeal joints and distal interphalangeal joints, in the hand orfoot.

To solve the problem of taking account of the anatomy, and particularlyof the internal shrinkage of the bone, the median zone is linked to atleast one of the fixation zones by a connecting zone.

To solve the problem of permitting implantation of the element followedby compression of the bone fragments, the fixation zones are made from ashape-memory material to be deformed by thermal and/or mechanicalaction.

To produce the fixation zones, which may be identical or not, varioustechnical solutions are feasible, according in particular to the type ofarthrodesis performed and the joints to be treated.

For example:

one of the fixation zones has two tabs or wings separable under theaction of the shape memory;

one of the fixation zones has a tab or rod which can be curved under theaction of the shape memory;

one of the fixation zones has, in its thickness, a slot for permittingdeformation by elasticity, or memory, under the action of the shapememory.

In one embodiment, the overall body has a flat cross-section.

BRIEF DESCRIPTION OF THE DRAWING

The invention is described below in greater detail in conjunction withthe figures of the drawings appended hereto in which:

FIG. 1 is a schematic plan view showing the placement of theintramedullary arthrodesis element of the invention between a proximalphalange and a median phalange to consolidate the proximalinterphalangeal joint;

FIG. 2 is a plan view of an embodiment of the arthrodesis element at thetime of its introduction;

FIG. 3 is a view corresponding to FIG. 2 showing the arthrodesis elementafter its implant to produce the compression;

FIG. 4 shows the placement of the element of the invention in a toe.

SPECIFIC DESCRIPTION

The arthrodesis element of the invention consists of an elongated body1. Each of the ends of the body 1 is conformed to produce a fixationzone 1 a linked to a fixation zone 1 b.

Between the two fixation zones 1 a and 1 b, at least one median zone 1 cis formed capable of withstanding shear and bending stresses. Ingeneral, the shear and bending stresses are applied to the bone site tobe consolidated. The shape of this median zone 1 c is adapted to theinternal shape of the bone. Its length is determined in order to allow aslight offset in the centering.

For information, and in a non-limiting manner, this median zone may havea rectangular cross-section measuring about 2 to 3 mm*1 to 1.5 mm and alength of about 3 to 5 mm for the foot and the hand.

The fixation zones 1 a and 1 b are conformed to prevent any rotationalmovement, resist tension, and maintain manual compression applied at thetime of the implant by the surgeon in order to reduce the site. Toobtain this result, the fixation zones 1 a and 1 b are made from ashape-memory material to be deformed by thermal action (tepid memory) ormechanical action (superelasticity) (see U.S. Pat. No. 5,958,159). Thegoal, in the fixation zones, considering their profile on the one handand the type of material on the other, is to permit an introduction intothe bone parts, particularly dorsally without a finger- or toe-tipapproach, on the one hand, and to produce a fixation in the bone portionin order to obtain or to maintain the desired compressive force, on theother. The fixation zones 1 a and 1 b are identical or not, according tothe type of bone and its morphology.

Depending on the type of arthrodesis performed, that is, the type ofinterphalangeal joint to be consolidated for example, the fixation zones1 a and 1 b may have different embodiments.

For example, one of the fixation zones 1 a has two tabs or wings thatare separable under a thermal action for example. Otherwise, thesefixation zones 1 a may have a single tab or rod which can be curvedunder the action of a memory of the component material. Otherwise, thefixation zone 1 b has, in its thickness, a slot to permit deformation byelasticity, under thermal action for example, and to maintain theposition by pressing on the length of the bone.

According to another feature of the invention, to take account of theanatomy of the various phalanges for example, that is the internalshrinkage of the bone (hourglass shape), the median zone 1 c is linkedto at least one of the fixation zones 1 b by a thinner connecting zone 1d.

Reference can be made to the figures of the drawings which show anembodiment of an intramedullar arthrodesis element.

In this embodiment, the body 1 has, at one of its ends, a fixation zone1 a in the form of two tabs or wings 1 a 1 1 a 2. This fixation zone 1 ais prolonged by a median zone 1 c of generally substantially triangularshape in a plan view. The median zone 1 c is connected to the other endfixation zone 1 b by a connecting zone 1 d having a generallyrectangular shape in a plan view. The fixation zone 1 b has, in itsthickness, a slot of generally oblong shape 1 b 1.

Reference can be made to FIG. 2 which shows the element at the time ofits introduction, that is before separation of the tabs 1 a 1 and 1 a 2,and the opening of the slot 1 b 1. For example, this configuration isobtained when the overall element is subject to a temperature much lowerthan that of the human body for example. Conversely, after implantation(FIG. 3), under the effect of body heat, the tabs 1 a 1 and 1 a 2separate, in the same way as the slot 1 b 1, concomitantly causing adeformation of the fixation zone 1 b.

It should be noted that the profile of the median zone 1 c preventspenetration when the site is reclosed.

In an alternative embodiment, the connecting zone 1 d can be split tobenefit from a swelling effect by shape memory and strengthening of theanchoring in the diaphyseal zone.

It should be recalled that the inventive element is ideal for thetreatment of the hammer- or claw-toe syndrome, by performing anarthrodesis in the phalanges P1 and P2 on the radii 2 to 5, whileobserving that such applications must not be considered as limiting, bymeans of essentially dimensional adjustments (finger reimplants,arthrodesis of the distal interphalangeal joint and of the proximalinterphalangeal joint of the hand, and the arthrodesis of the big toe).

Obviously, the entire arthrodesis element of the invention may haveconstructive features suitable for improving the fixation andcompression in particular.

For example:

notches on the tabs on one of the sides for better fixation in theethmoid bone;

wavy tabs implanted (straight before implant)

to permit shortening and hence an additional compression of thearthrodesis site compared with a simple fixation;

a tapered central zone to avoid undesirable

penetration of the implant at the time when the site is to be closed.

For information, the memory used is preferably a tepid memory, so thatheating is unnecessary because of the lack of access. The opening beginsat above 15 to 20° C. and stops at about 30 to 35° C.

The operating technique remains conventional.

The invention claimed is:
 1. A fixation device comprising: a median zonehaving a substantially triangular shape; a first fixation zone includingfirst and second tabs that, in a separated configuration, extend awayfrom each other from an end of the median zone, the first fixation zonehaving a first region adjacent the median zone and a second regionadjacent the first region; wherein, within the first region of the firstfixation zone, an inner surface of each of the first and second tabs ofthe first fixation zone extends outwardly and proximally from the medianzone to a first point on each of the first and second tabs to form anarch extending continuously from the first point on the first tab to thefirst point on the second tab, and from each of the first points, theinner surface of each of the first and second tabs extends toward asecond point, and within the second region of the first fixation zone,the inner surface of each of the first and second tabs of the firstfixation zone extends outwardly from each second point to a respectivethird point so that the inner surface of each of the first and secondtabs from the second point to the third point is arcuate and convex. 2.The device of claim 1, wherein each tab in a first fixation zoneincludes at least one outwardly projecting barb adapted to engage bone,the barb including a decline toward the distal end of the fixationdevice.
 3. The device of claim 1, further comprising a generallyrectangular connecting zone adjacent the median zone.
 4. The device ofclaim 1, further comprising a second fixation zone including first andsecond tabs extending outwardly in a proximal direction away from adistal tip.
 5. The device of claim 4, wherein the second fixation zoneis positioned at one end of the median zone and the first fixation zoneis positioned at an opposite end of the median zone, wherein both thefirst and second tabs of the second fixation zone and the first andsecond tabs of the first fixation zone extend proximally.
 6. The deviceof claim 1, wherein the first and second tabs of the first fixation zonecomprise a first width in the separated position.
 7. The device of claim6, wherein the first and second tabs of the first fixation zone comprisea second width in an implantable position that is narrower than thisfirst width.
 8. The device of claim 4, wherein the first and second tabsof the second fixation zone have a first width in an open position. 9.The device of claim 8, wherein the first and second tabs of the secondfixation zone have a second width in an implantable position that isnarrower than the first width.
 10. A fixation device comprising: a bodyextending between a proximal end and a distal end including a proximalfixation zone, a distal fixation zone and a median zone positionedbetween the proximal and distal fixation zones, the proximal fixationzone including a first tab and a second tab that, in a separated zone,extend from a proximal end of the median zone in a radially outwarddirection to a first tab end and a second tab end, wherein an innersurface of the first and second tabs forms a first length extending fromadjacent the median zone to a first point on each of the first andsecond tabs with an increasing slope along the first length, forms asecond length along each of the first and second tabs with a decreasingslope from the first point to a second point, and forms a third lengthalong each of the first and second tabs with an increasing slope fromthe second point to the respective first tab end and second tab end. 11.The device of claim 10, wherein the decreasing slope from the firstpoint to the second point defines a concave surface.
 12. The device ofclaim 10, wherein the increasing slope from the second point to thefirst and second tab ends defines a convex surface.
 13. The device ofclaim 10, wherein the first tab end and second tab end each form an apexof each of the first and second tabs and, from the apex, the innersurface of each tab extends to a barb positioned on an outer surface ofeach of the first and second tabs.
 14. The device of claim 10, whereinthe distal fixation zone includes a first tab and a second tab extendingin a radially outward direction from a distal-most end towards themedian zone.
 15. The device of claim 14, wherein the first and secondtabs of the proximal fixation zone and the first and second tabs of thedistal fixation zone both extend radially outwards in a proximaldirection.
 16. The device of claim 15, further comprising a generallyrectangular connecting zone positioned between the median zone and thedistal fixation zone.
 17. A fixation device comprising: a monolithicbody extending between a proximal end and a distal end including aproximal fixation zone, a distal fixation zone and a median zonepositioned between the proximal and distal fixation zones, the proximalfixation zone including a first tab and a second tab, the first andsecond tabs each having a first region adjacent a second region, and thedistal fixation zone including a first tab and a second tab extending ina radially outward direction from a distal-most end towards the medianzone, wherein the proximal fixation zone has an open position, in theopen position an inner surface of the first region of the first andsecond tabs forms a convex surface and an inner surface of the secondregion of the first and second tabs forms a concave surface.
 18. Thefixation device of claim 17, wherein the proximal fixation zone has animplantable position, in the implantable position the inner surface ofthe second region of the first and second tabs is substantially linear.19. The fixation device of claim 17, wherein the convex surface isproximal to the concave surface.
 20. The fixation device of claim 17,wherein the inner surface of the first region of the first and secondtabs forms an arch.